Wet beneficiating of phosphate ores



May 7, 1963 J. F. HAsEMAN ETAL 3,088,590

wm' BENEFICIATING oF PHosPHATE om-:s

Filed sept. 2, 1960 United States Patent Ol'ice 3,088,590 Patented May 7, 1963 This invention relates to the beneilciation of phosphate ores. More particularly, the invention relates to a process for the wet concentration of unsized phosphate minerals pursuant to which a substantial portion of the phosphate values of the ore are recovered.

Wet beneciation of phosphate ores has long been a common expedient widely practiced in the industry. Ore ground to substantial liberation of its mineral values, for example to l2 mesh, conventionally is sized by means of classifiers, screens, trommels, hydroseparation and the like to provide a 12 +35 fraction and -35 +150 or 20() mesh fraction. The coarser fraction, generally considered to be too coarse for froth ilotation, is beneficiated by means of spirals, shaking tables and the like. The finer -35 mesh fraction is subjected to froth flotation.

Early practice in the concentration of phosphate ores comprising apatite or lluorapatite and a siliceous gangue entailed reagentizing the liberated finely divided ore with an anionic reagent effective selectively to coat at least a portion of the surfaces of the phosphatic particles present, followed by concentration of the reagentzed ore by froth flotation to provide a phosphate concentrate as a froth product and a silica tail as a depressed or sink product. At acceptable levels of recovery, particularly from relatively low grade ores, the grade of the concentrates was objectionably low.

An alternative procedure known to the early art embraced reagentizing the liberated phosphate ore with a cationic reagent effective selectively to coat at least a portion of the surfaces of the silica particles, followed by froth llotation to produce a silica tail as a froth product and a phosphate concentrate depressed or sink product. Such a procedure likewise failed to afford a concentrate of satisfactory grade and recovery.

The phosphate industry, accordingly, resorted to a cornbined process pursuant to which the liberated phosphate ores were subjected to both an anionic ilotation and a cationic tlotation in an effort to achieve satisfactory recovery of the phosphate values.

The development which led to a first anionic flotation followed by a cationic llotation is described in detail in Crago Patent 2,293,640, and in a plurality of subsequently issued patents, including Duke-2,461,813, Duke- 2,661,842, and Hunter-2,750,036. Such llotation proC- esses reilect the recognition by the art that only the more finely divided ore, e.g., 35 mesh, is well suitedfor ilotation.

A second line of development for the otation of phosphate ores, wherein the phosphate ore is subjected to a rst cationic llotation and then to a subsequent anionic flotation, is exemplied, inter alia, in Trinitron- 2,222,- 728, Greene-2,288,237, and Hollingsworth-2,815,859. Again the processes were practiced on a rather finely divided ore, generally -20 mesh or finer.

Processes, such as the above, must relay on an arcuate sizing of the liberated ore to achieve eillcient separation. In practice, however, it is extremely ditlicult to achieve an accurate sizing of the ore. As a threshold matter, much of the ground ore is characterized by a size of about 35 mesh. Moreover, variations in the shape and specic gravity of the particles and their tendency to blind screens further contribute to an inaccurate sizing and ultimately to a lower recovery of the phosphate values of the ore.

.desirable constituent of the ore.

Typical screen sizings of a liberated phosphate ore are as follows:

Coarse Fine Mesh size traction, fraction, percent percent +35 l0-4l) Erl -35 Hill 95-85 It will be apparent such processing, requiring extensive sizing equipment, does not provide an eillcient sizing of the ore.

It is a primary object of this invention to provide a method for the wet benellciation of phosphate ores pursuant to which high recoveries of phosphate values are realized.

It is another object of this invention to provide a method for the wet beneliciation of unsized phosphate ores pursuant to which a high proportion of the phosphate values are recovered.

It is a further object of this invention to provide a method for the wet benellciation of phosphate ores which does not require that the entire ground ore be subjected to a preliminary sizing.

In accordance with this invention, there is provided a method of beneficiating phosphate ore, which comprises:

(l) Subjecting unsized liberated phosphate ore to froth flotation in the presence of a cationic reagent to provide a phosphate-rich underflow and a silica containing overflow.

(2) subjecting the underow from (l) to froth llotation in the presence of an anionic flotation reagent to provide a phosphate-rich overilow concentrate and an underllow.

(3) Subjecting the underllow from (2) to gravity separation to provide a phosphate-rich concentrate and a silica tail.

This invention at the same time eliminates the preliminary sizing operation and improves the recovery of phosphate values from the ore. Accordingly, it provides a simplified process that recovers optimum quantities of the Moreover, because the cationic lloat is accomplished rst, the amount of anionic reagentrequired may be reduced and the acid scrub to remove anionic reagent often may be omitted.

From the standpoint of equipment requirements, this invention eliminates the preliminary screens or like sizing equipment and may reduce the gravity separation capacity requirement.

The process of this invention effectively combined froth flotation with gravity separation to provide a process which efficiently beneficiates unsized phosphate ore. In contrast to the combined cationic and anionic flotation processes referred to earlier, the process of this invention utilizes the dual ability of a Vflotation unit to recover a desired concentrate and Yto effect a sizing of the ore being processed. `Predominantly silica lines are removed from the ore in the cationic flotation, and the liner phosphate particles are removed Vfrom the ore in the anionic llotation. This combined processing provides an underflow from the anionic llotatjon, which contains significant amounts of the coarser particles of both the phosphate values and the silica values of the ore. The underllow most effectively can be processed by gravity separation. Accordingly, the process of this invention differs in principle from those processes which utilize essentially only froth ilotation as exemplified, for example, by Crago or by Tartaron described above.

Since the process of this invention is designed to treat an unsized ore so as to yield a product stream containing a significant proportion of the coarser particles of the ore, it will be apparent that the process of this invention also differs in principle from processes such as are exemplified by Evans-2,553,905 wherein the ore is subjected to a single flotation before gravity separation merely to eliminate a portion of one of the values.

This invention is generically applicable, without limitation, to phosphate ores amenable to wet concentration. Specific ores contemplated include Florida pebble phosphate, the various Tennessee phosphates, hard rock phosphates indigenous to the western United States, and the various foreign phosphate ores such as Moroccan phosphates.

The phosphate ore to be treated in accordance with the process of this invention is preliminarily ground employing a standard grinding apparatus to a desired mesh size generally of at least about 10, preferably about 12, and is washed to remove slirnes and provide a ground ore characterized by a mesh size of about ior l2, +150 or 100. Since the process of this invention efficiently processes such coarsely ground ores, the practice of this invention eliminates the need for extensive grinding to provide a very fine particle size.

The ground deslimed ore then is reagentized employing any of the cationic or positive ion agents known to the art. Such reagents include, inter alia, the higher aliphatic amines and their salts with water-soluble acids; the esters of amino alcohols with high molecular weight fatty acids and their salts with water-soluble acids; the higher alkyl- O-substituted isoureas and their salts with water-soluble acids; the higher aliphatic quaternary ammonium bases and their salts with water-soluble acids; the higher alkyl pyridinium water-soluble acids; the higher alkyl quinoliniurn salts of watersoluble acids; and the like.

The reagentized ore is subjected to froth flotation employing any of the flotation equipment known to the art. The flotation is effective to remove, in the overflow, a substantial portion of the finer silica particles of the ore.

The underflow from the flotation unit, containing substantially all of the phosphate values of the ore, may, if desired or appropriate, be treated with a material such as sodium hypochlorite or the like and washed to remove the cationic reagent. While such treatment tends to irnprove the efliciency of the later flotation stages, it is not essential and significant recoveries can be achieved without de-reagentizing the ore after the cationic flotation.

The underflow next is subjected to froth flotation in the presence of an anionic flotation reagent to provide a phosphate overflow which contains a substantial amount of the finer phosphate particles of the ore. The underflow from the anionic flotation will contain both phosphate and silica particles and will contain a substantial proportion of the larger size particles of the original ore.

The invention generically embraces the anionic or negative ion reagents known to the art. Such reagents include, inter alia, fatty acids or fatty acids soaps, particularly mixed fatty acids or soaps thereof; fatty acids or soaps of acids derived from natural sources such as tall oil soaps and floating soap; fatty acids or soaps of acids derived from animal and vegetable fats; esters of inorganic acids with high molecular weight alcohols; and the like. Conventionally, such anionic reagents are applied in solution or in a dispersion in a carrier medium such as a hydrocarbon oil, normally kerosene or fuel oil. One widely used specific reagent combination comprises about one to about three parts tall oil, from about two to about four parts kerosene, and from about two to about four parts Bunker C fuel oil.

The underflow from the anionic flotation may be subjected, if it is desired or appropriate, to scrubbing with water or more desirably with a mineral acid such as sulfuric acid to remove the anionic reagent. The underflow then may be reagentized with a. cationic reagent such as described above in order to increase the efficiency of the gravity separation. While the removal of the anionic reagent tends to improve the efficiency of the gravity separation when the ore is reagentized with cationic agents, such removal is not essential.

Alternately, the underflow from the anionic flotation may be subjected to gravity separation containing only that amount of anionic reagent which is present as a result of the anionic flotation. If desired, of course, an additional amount of anionic agent can be added to the ore.

The underflow is subjected to a gravity separation to provide a second phosphate-rich concentrate product and a silica tail. The gravity separation may be carried out employing any of the means known to the art, including without limitation, spirals, tables, belts and the like. Spirals, for example Humphrey spirals, are found to be particularly appropriate for the gravity separation.

While each flotation has been described as if it were conducted in a single flotation unit, it will be apparent that a plurality of units in parallel or in series may be employed for each flotation stage. Thus, for example, the phosphate concentrate overflow from the anionic flotation can be subjected to a cleaner anionic flotation. In this event, the underflow from each unit is combined and subjectcd to gravity separation.

The control of flotation air rates, solids content of the slurry in the flotation unit and similar process conditions are within the skill of the routineer. Tests indicates that the cationic reagent most appropriately may be employed in amounts of at least 0.2 pound per ton and desirably in amounts of at least about 0.3 pound per ton. The cationic underflow most appropriately may be conditioned with an anionic reagent in amounts of at least about 0.2 pound `per ton and preferably of at least about 0.5 pound per ton. These reagents may be employed in amounts up to l0 pounds per ton or more if desired. The use of large quantities of reagent, of course, tends to effect adversely the economics of the process.

The method of this invention is demonstrated by the flow sheet in the attached drawing. FIGURE 1 represents a diagrammatic flow sheet of one preferred method of this invention.

Referring to FIGURE l, the deslimed unsized phosphate ore (-10 -j-l50) from feedbin 1 is mixed with a flotation reagent composition such as a long chain aliphatic amine and delivered to flotation unit 2. The overflow from flotation unit 2 will be composed primarily of silica and heavy minerals, and may either be discarded or further processed to recover heavy minerals, feldspar or the like. The underflow from flotation unit 2 is thickened, for example to a solids content of at dewatering station 3, mixed with sodium hypochlorite at mixing station 4 and washed at washing station 5. The sodium hypochlorite treatment may be omitted if desired. The underflow then is conditioned with an anionic flotation reagent such as tall oil and subjected to anionic flotation in flotation unit 6. The phosphate-rich overflow from flotation unit 6 may be subjected to a cleaner flotation in flotation unit 7 to provide a final phosphate overflow product. The underflows from flotation units 6 and 7 containing coarse phosphate and coarse silica particles are combined, dewatered at dewatering station 8, and, if desired, mixed with a mineral acid such as sulfuric acid at mixing station 9. Following a wash in washing station 10, the underflow may be conditioned with a cationic reagent. Alternatively, stations 9 and 10 can both be omitted and the `underflow subjected to gravity separation with or without added anionic reagents. The gravity concentration 11 rnost desirably is effected by means of spirals to provide a phosphate-rich concentrate product and a silica tail.

The following examples are included in order more fully to demonstrate the practice of this invention. These examples are included for illustrative purposes only and are in no way intended to limit the scope of the invention.

EXAMPLE I Deslimed phosphate ore +150 containing about 2,0% +35 mesh material) was subjected to froth flotation employing 0.25 1b./ton of an amine reagent (50% ali-z,

Bunker C nel oil and 0.5 lb,/ton NaOH and subjected to an agglomerate tabling on a shaking table. The results of this test, based on table middlings containing 50% of the phosphate values are reected in Table 4.

phatic amines 50% rosin amines) and 0.20 lb./ton 5 Table 4 NaOH.

The concentrate and tail analyzed as follows: W i ht Ssayxpmem U 'L P t e g Il! q 91091'1 Table I Product percent BPL recovery 10 BPL nerd BPL insel r Assay percent l eight' Flotanon eone-. 25.9 73.7 2.9 19,05 53.3 gm' p BPL Ins, Tab1ec5nc 13.5 7a2 9,47 31,5 o Fioranon 1511s--. 47, 2 2A o 0. 94 3,1 r T5hle1511s.-, 13.4 4.7 0,63 2.1 Concentrate 21,570 52.82 53. 97 27.45 10 'rail 19,270 47,18 1,98 96,62 Total 10o-3 30-12 10M The concentrate was de-reagemized with 1.5 lbs/1011 The above examples demonstrate that a very high of sodium hypochlorite, washed and conditioned at 70% recovery of phosphate values may be achxeved 1n accordsolid-s with 0.55 lb./ton of tall oil and 0.5 lb./ton NaOH ance with the practice of this invention. Generally, Vthe for 1 minute. A `rougher froth flotation fofliowed by a process of this invention will permit the recovery of 90% cleaner froth iiotation of the rougher overow produced to 9,5% or more oef the phosphate values of ore originally the following streams, containing 35 to 40% phosphate values. In contr-ast, a Table 2 standard process which initially screens comparable ore and employs gravity separation for the +35 mesh mate- Stream welghbiwcight, Assay Percent Units Units rial U01' many recovers only 85% t0 90% 0)? the P hOSPh'agms- Iperm BPL m01 BPL USOL values. Moreover the practice of this invention may permit la reduction in the anionic flotation reagent remsner con@ 5,272 48.79 73. 71 2,21 35,95 1.42 110111511911511 5,0135 35.112 25. 55 es, 52 9.40 22.50 qmemenls cleaner 1511 2, 577 15.79 54. 41 27.95 8.59 4.41 30 Since modncations of th1s invention will be apparent to one skilled in the art, it is intended that this invention The combined tails then were subjected to spiral separbg limite@ oni? 'by the Scope 0f the appended Claimsation to provide a final concentrate. We Claim:

EXAMPE H 1. The method of benefciating an unsized phosphate ore fraction which comprises: A screen analysis of a concentrate obtained by the cat- (1) Subjecting an unszed liberated deslimed phosionic flotation of Example l is reflected in Table 3, phate ore fraction containing particles of a mesh size Table 3 Weight Cum, Percent Units Percent Percent Size Weight percent weight BPL BPL or BPL insol.

percent 7.5 1,5 i 1,5 70.03 1,75 3.14 5. 41 1s. 0 5. 7 5, 2 es. 55 2, 47 4. 44 1n. 41 5 5. 9 12.1 55. o7 a. sn e, s2 25. 95 54. 0 1s. 2 25. a 42. 2s 5. 5s 1o, o2 44. 07 10s, o 22. s 47. 5 411. 54 1u, ss 1s, 54 as. 11 115. o 23, 5 70.11 55. 51 12. 95 23. 2s 25.18 114. 5 23. 7 94. 5 e4. a5 15. 25 27,35 14. ss 25. o 5, 4 10o s4. 57 5. 49 e. 27 12. 56

Tota1. 484.5 100,0 555s 100 Table 3 demonstrates that the +35 mesh fraction,

originally about 20%, constitutes about 25% of the cati- 5 EXAMPE III A low grade Florida phosphate ore was ground to -10 mesh and was Washed to remove -150 Vmesh slimes to provide an ore containing about 20% +35 mesh material, The ore then was subjected to froth flotation in the presence of 0.25 lb./ton of a cationic flotation reagent aliphatic amines and 50% rosin amines), 0,50 lb./ton of kerosene and 0.25 lb./ton of NaOH. The underflow from the cationic flotation was washed with 1.5 `lbs./ ton of sodium hypochlorite and subjected to additional froth flotation in the presence of 0.55 lb./ton of tall oil, 0.55 lb./ton of kerosene, 1.1 lbs/ton of Bunker C fuel oil, and 0.5 lb./ton NaOH, The overflow phosphate concentrate was cleaned once by reotation without reagent. The combined underflow rom the rougher and cleaner anionic flotation were washed with l0 lbs/ton of H2SO4. The washed underiiow was then conditioned with 0.6 lb./ton of tall oil, 0.6 lb./ton of kerosene, 1.2 lbs/ton of from about 10 mesh to about 200 mesh to froth flotation in the `presence of a cationic reagent to provide a phosphate-rich underflow and a silica containing overflow;

(2) subjecting the underflow `from (l) to froth otation in the presence of an anionic flotation reagent to provide a phosphate-rich overflow concentrate and yan underflow; and

(3) Subjecting the underflow from (2) to gravity separation to provide a phosphate-rich concentrate and a silica tail.

2. The method of claim 1 wherein the cationic reagent is aliphatic amine.

3. The method of claim l wherein the `anionic reagent is selected from the group consisting of fatty acids and fatty acid soaps.

4. The method of beneciating `an unsizted phosphate ore fraction which comprises:

(1) subjecting an unsized liberated deslimed phosphate ore fraction containing particles of a mesh size of lfrom about 10 mesh to about 200 mesh to froth flotation in the presence of a cationic reagent to provide a phosphate-rich underflow and a silica containing overflow;

(2) Subjecting the underflow from (1) to froth {iotation in the presence of an anionic otation reagent to provide a phosphate-rich overow concentrate and an underflow,

(3) subjecting the overilow from (2) to froth flotation to provide a phosphateaich overow concentrate and an underow; and

(4) Subjecting `the underow from (2) and (3) to gravity separation to provide a phosphate-rich concentrate and a silica tail.

5. The method of claim 4 wherein the cationic reagent is aliphatic amine.

6. The method of claim 4 wherein the anionic reagent is selected from the group consisting of fatty `acids and fatty acid soaps.

7. The method of claim 4 wherein the unsized ore fraction is characterized by a mesh size range of -12 +150.

8. The method of beneciating an unsized phosphate ore fraction which comprises:

(1) Subjecting an unsized liberated deslimed phosphate ore fraction containing particles of a mesh size of from about 10 mesh to about 200 mesh to froth otation in the presence of a cationic reagent to provide a phosphate-rich underilow and a silica containing overflow;

(2) Contacting the underflow from (1) with sodium hypochlorite to remove the cationic reagent;

(3) subjecting the treated underflow from (1) to froth ilotation in the presence of `an anionic flotation reagent to provide a phosphate-rich overow concentrate `and an underow;

(4) Subjecting the phosphate-rich overow from (3) to froth flotation to provide a phosphate-rich overlow concentrate and an underow;

(5) Subjecting the underows from (3) and (4) to treatment with a mineral acid to remove the anionic reagent, and

8 (6) Subjecting the treated underows from (3) and (4) to gravity separation to provide a phosphaterich concentrate and a silica tail. 9. The method of claim 8 wherein the cationic reagent is an aliphatic amine and the anionic reagent is selected from the group consisting of fatty acids and fatty acid soaps.

10. The method of claim 9 wherein the unsized phosphate ore fraction is characterized by a mesh size range of about -12 +150.

11. The method of claim 1 wherein said unsized liberated deslimed phosphate ore fraction contains particles of a mesh size of from about 12 mesh to about 150 mesh.

12. The method of claim 1 wherein said unsized liberated deslimed phosphate ore fraction contains particles of a mesh size of from about 14 mesh to `about 150 mesh.

13. The method of claim 4 wherein said unsized liberated deslimed phosphate ore fraction contains particles of a mesh size of from about 14 mesh to about 150 mesh.

14. The method of claim 8 wherein said unsized liberated deslimed phosphate ore fraction contains particles of a mesh size of from about 14 mesh to about 150 mesh.

References Cited in the le of this patent UNITED STATES PATENTS 2,222,728 Tartaron Nov. 26, 1940 2,553,905 Evans May 22, 1951 2,614,692 Lawver Oct. 21, 1952 2,811,254 McGarry Oct. 29, 1957 2,914,173 Le Baron Nov. 24, 1959 2,922,522 Penske Jan. 26, 1960 2,952,360 Oberg Sept. 13, 1960 2,970,688 Uhland Feb. 7, 1961 3,013,664 Hollingsworth Dec. 19, 1961 

1. THE METHOD OF BENEFICIATING AM IMSOZED ORE FRACTION WHICH COMPRISES: (1) SUBJECTING AN UNSIZED LIBERATED DESLIMED PHOSPHATE ORE FRACTION CONTAINING PARTICLES OF A MESH SIZE OF FROM ABOUT 10 MESH TO ABOUT 200 MESH TO FROTH FLOTATION IN THE PRESENCE OF A CATIONIC REAGENT TO PROVIDE A PHOSPHATE-RICH UNDERFLOW AND A SILICA CON TAINING OVERFLOW; (2) SUBJECTING THE UNDERFLOW FROM (1) TO FROTHFLOATTION IN THE PRESENCE OF AN ANIONIC FLOTATION REAGENT TO PROVIDE A PHOSPHATE-RICH OVERFLOW CONCENTRATE AND AN UNDERFLOW; AND 